The present invention relates to a display driver and an electronic instrument.
In recent years, a display panel has been increasingly demanded accompanying an increase in functionality of electronic instruments. As a drive method for a display panel, various methods have been proposed. A driver circuit disclosed in Japanese Patent Application Laid-open No. 7-281636 has been known as an example. Japanese Patent Application Laid-open No. 7-281636discloses a circuit which drives a display panel by using 10 column drivers when the display panel includes 640×480 pixels, for example. A calculation circuit is provided in each column driver. Since the calculation circuit simultaneously processes display data for 7 lines×480 columns read from a memory, the calculation circuit becomes complicated and the circuit area is increased.
Moreover, since the amount of display data is increased as the resolution of the display panel is increased, the driver circuit of the display panel also becomes complicated. If the circuit becomes complicated, manufacturing cost is increased due to an increase in the chip area and the design period. In particular, the area of the calculation circuit is considerably increased in the driver circuit disclosed in Japanese Patent Application Laid-open No. 7-281636.
According to the configuration of the display memory disclosed in Japanese Patent Application Laid-open No. 7-281636, voltage may be applied to a word gate of a transistor which makes up the display memory when an unexpected voltage is applied to a wordline of the display memory, whereby erroneous data may be written into the display memory. In this case, one vertical line is displayed on the display panel, and the erroneous display state continues until the display memory is rewritten.